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as the amount of moisture may be a factor in the results obtained. 

 These instances are mentioned as illustrations of the fact that 

 in etiolation phenomena we are dealing with a growth in which 

 the propelling forces are so weak and so simplified, compara- 

 tively speaking, that as a result the slightest cause may lead to 

 marked deviations. This may explain the variations that were 

 noticed in a series of etiolated seedlings of Qiiercus velutina. In 

 one experiment a few of the plants showed a second growth, that 

 might be interpreted as adaptive, although the majority perished 

 before or after the usual number of scales and leaves were devel- 

 oped. In another case several plants showed a continued growth 

 without any interruption, and finally developed the same number 

 of leaves as were found upon the plants that exhibited the re- 

 newal of growth. They developed, however, a greater length of 

 stem, and the leaves were not clustered as in the first case, but 

 were separated by fairly regular intervals. In the second ex- 

 periment, the plants were germinated in feeble light, but were re- 

 moved to the dark room as soon as the first shoots appeared 

 above the soil and before there was any appearance of chloro- 

 phyll. It is very possible that the presence of enzymes and the 

 availability of foods made possible by the conditions of germina- 

 tion may account for the difference of growth. 



In the same way other reactions of plants in darkness may pos- 

 sibly be explained. For example, I have noticed the twining 

 habit of several plants, as recorded by Noll. The sweet potato 

 grows remarkably well in the dark and the etiolated stems begin 

 to twine when they have attained a length of a meter or more. 

 This phenomenon is also strongly marked in young shoots of 

 Falcata comosa — a plant that is especially suitable to experi- 

 mentation since it reaches a normal development in the laboratory 

 where the light is often not of the best and shows striking con- 

 trasts with the etiolated plants. However, it should be re- 

 marked that these plants were exposed to an occasional illumi- 

 nation of the electric light for purposes of examination and 

 watering. Several plants of Falcata that were grown this spring 

 under a can in the dark room and not exposed to light were 

 found, when finally examined, to have developed shoots that 



